Messages in this thread | | | Subject | Re: [PATCH v2 3/3] vfio/pci: Don't probe devices that can't be reset | From | David Daney <> | Date | Fri, 18 Aug 2017 08:57:09 -0700 |
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On 08/18/2017 07:12 AM, Alex Williamson wrote: > On Fri, 18 Aug 2017 15:42:31 +0200 > Jan Glauber <jan.glauber@caviumnetworks.com> wrote: > >> On Thu, Aug 17, 2017 at 07:00:17AM -0600, Alex Williamson wrote: >>> On Thu, 17 Aug 2017 10:14:23 +0200 >>> Jan Glauber <jglauber@cavium.com> wrote: >>> >>>> If a PCI device supports neither function-level reset, nor slot >>>> or bus reset then refuse to probe it. A line is printed to inform >>>> the user. >>> >>> But that's not what this does, this requires that the device is on a >>> reset-able bus. This is a massive regression. With this we could no >>> longer assign devices on the root complex or any device which doesn't >>> return from bus reset and currently makes use of the NO_BUS_RESET flag >>> and works happily otherwise. Full NAK. Thanks, >> >> Looks like I missed the slot reset check. So how about this: >> >> if (pci_probe_reset_slot(pdev->slot) && pci_probe_reset_bus(pdev->bus)) { >> dev_warn(...); >> return -ENODEV; >> } >> >> Or am I still missing something here? > > We don't require that a device is on a reset-able bus/slot, so any > attempt to impose that requirement means that there are devices that > might work perfectly fine that are now excluded from assignment. The > entire premise is unacceptable. Thanks,
You previously rejected the idea to silently ignore bus reset requests on buses that do not support it.
So this leaves us with two options:
1) Do nothing, and crash the kernel on systems with bad combinations of PCIe target devices and cn88xx when vfio_pci is used.
2) Do something else.
We are trying to figure out what that something else should be. The general concept we are working on is that if vfio_pci wants to reset a device, *and* bus reset is the only option available, *and* cn88xx, then make vfio_pci fail.
What is your opinion of doing that (assuming it is properly implemented)?
Thanks, David Daney
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